Outcomes of 3 or 4 Horizontal Muscles Surgery in Large-Angle Exotropia

Purpose To evaluate motor and sensory outcomes of 3 or 4 horizontal muscles surgery for the treatment of large-angle exotropia and to evaluate factors influencing the success rate and the relationship between initial postoperative and final motor outcomes. Design A retrospective analytical study. Methods Medical records of patients with primary large-angle exotropia [>50 prism diopters (PD)] who had 3 or 4 horizontal muscles surgery were reviewed. Motor outcomes were categorized as successful (esotropia 1-8 PD, orthotropia or exotropia 1-10 PD), acceptable (exotropia 11-20 PD), and poor (esotropia >8 PD or exotropia >20 PD). Results were evaluated only at the last follow-up visit if patients were followed up for less than 2 years. Those who were followed up for more than 2 years were evaluated at both the 2-year and final follow-up visits. Factors influencing the success rate and the relationship between initial postoperative and final motor outcomes were analyzed. Results A total of 36 patients were enrolled in this study. The median follow-up time was 18 months (range, 3-60 months). The success rate was 69% at the last follow-up and 75% at the follow-up at 2 years, respectively. Stereopsis improved in 43% at the last follow-up and 56% at 2 years. Initial postoperative deviation was found to correlate with the success rate at the last follow-up (P = 0.018). Initial postoperative overcorrection of 8 to 14 PD had the highest possibility of gaining successful final motor outcomes. Conclusions Three or 4 horizontal muscles surgery in large-angle exotropia can achieve successful motor outcomes and improve stereopsis. Surgeons should aim for initial overcorrection in order to maximize long-term success.